Plutonium in the environment: key factors related to impact assessment in case of an accidental atmospheric release

International audienceThis paper deals with plutonium and key factors related to impact assessment. It is based on recent work performed by CEA which summarize the main features of plutonium behaviour from sources inside installations to the environment and man, and to report current knowledge on the different parameters used in models for environmental and radiological impact assessment. These key factors are illustrated through a case study based on an accidental atmospheric release of Pu in a nuclear facility

Evolution of the UV LF from z~15 to z~8 Using New JWST NIRCam Medium-Band Observations over the HUDF/XDF

Here we present the first constraints on the prevalence of z>10 galaxies in the Hubble Ultra Deep Field (HUDF) leveraging new NIRCam medium-band observations taken with JWST. These NIRCam observations probe redward of 1.6microns, beyond the wavelength limit of HST, allowing us to search for galaxies to z>10. These observations indicate that the highest redshift candidate identified over the HUDF with HST, UDFj-39546284, has a redshift of z=12.0+/-0.1, as had been suggested in multiple analyses of the HUDF12/XDF data. This source thus appears to be the most distant galaxy discovered by HST in its more than 30 years of operation. Additionally, we identify nine other z~8-13 candidate galaxies over the HUDF, two of which are entirely new discoveries and appear to lie at z~11 and z~12. We use these results to characterize the evolution of the UV luminosity function (LF) from z~15 to z~8.7. While our LF results at z~8.7 and z~10.5 are consistent with previous findings over the HUDF, our new LF estimates at z~12.6 are substantially higher than other results in the literature, potentially pointing to a milder evolution in the UV luminosity density from z~12.6. We emphasize that our LF results are uncertain given the small number of sources in our z~12.6 selection and limited volume probed. The new NIRCam data also indicate that the faint z~8-13 galaxies in the HUDF/XDF show very blue UV-continuum slopes beta~-2.7, high specific star formation rates ~24.5 Gyr$^{-1}$, and high EW (~1300A) [OIII]+Hbeta emission, with two z~8.5 sources showing [OIII]+Hbeta EWs of ~2300 Angstroms.Comment: 19 pages, 14 figures, 7 tables, submitted to MNRAS, with some minor typos correcte

HIV-1 Gag-Pol Sequences from Ugandan Early Infections Reveal Sequence Variants Associated with Elevated Replication Capacity.

The ability to efficiently establish a new infection is a critical property for human immunodeficiency virus type 1 (HIV-1). Although the envelope protein of the virus plays an essential role in receptor binding and internalization of the infecting virus, the structural proteins, the polymerase and the assembly of new virions may also play a role in establishing and spreading viral infection in a new host. We examined Ugandan viruses from newly infected patients and focused on the contribution of the Gag-Pol genes to replication capacity. A panel of Gag-Pol sequences generated using single genome amplification from incident HIV-1 infections were cloned into a common HIV-1 NL4.3 pol/env backbone and the influence of Gag-Pol changes on replication capacity was monitored. Using a novel protein domain approach, we then documented diversity in the functional protein domains across the Gag-Pol region and identified differences in the Gag-p6 domain that were frequently associated with higher in vitro replication

Characterization of Near Full-Length Transmitted/Founder HIV-1 Subtype D and A/D Recombinant Genomes in a Heterosexual Ugandan Population (2006-2011).

Detailed characterization of transmitted HIV-1 variants in Uganda is fundamentally important to inform vaccine design, yet studies on the transmitted full-length strains of subtype D viruses are limited. Here, we amplified single genomes and characterized viruses, some of which were previously classified as subtype D by sub-genomic pol sequencing that were transmitted in Uganda between December 2006 to June 2011. Analysis of 5' and 3' half genome sequences showed 73% (19/26) of infections involved single virus transmissions, whereas 27% (7/26) of infections involved multiple variant transmissions based on predictions of a model of random virus evolution. Subtype analysis of inferred transmitted/founder viruses showed a high transmission rate of inter-subtype recombinants (69%, 20/29) involving mainly A1/D, while pure subtype D variants accounted for one-third of infections (31%, 9/29). Recombination patterns included a predominance of subtype D in the gag/pol region and a highly recombinogenic envelope gene. The signal peptide-C1 region and gp41 transmembrane domain (Tat2/Rev2 flanking region) were hotspots for A1/D recombination events. Analysis of a panel of 14 transmitted/founder molecular clones showed no difference in replication capacity between subtype D viruses (n = 3) and inter-subtype mosaic recombinants (n = 11). However, individuals infected with high replication capacity viruses had a faster CD4 T cell loss. The high transmission rate of unique inter-subtype recombinants is striking and emphasizes the extraordinary challenge for vaccine design and, in particular, for the highly variable and recombinogenic envelope gene, which is targeted by rational designs aimed to elicit broadly neutralizing antibodies

Les méthodes et les limites de la dosimétrie après contamination interne

The assessment of absorbed, equivalent and effective doses after internal exposure is based on activity measurement by in vivo counting or bioassay. A dose value is derived from this measurement by means of biokinetic and dosimetric models which describe the behaviour of radionuclides in the body of a reference man and the subsequent deposition of energy. To enforce regulatory dose limits, monitoring programs are designed. The doses can be estimated from the measurement data according to a standard procedure as proposed by the IDEAS group. However, a significant uncertainty is associated with the dose estimate, due to the uncertainties of measurement, to the incomplete knowledge of the conditions of exposure and to the imperfect realism of the models. In addition to this uncertainty, the extrapolation to low dose of biological effects observed at higher dose, the chemical toxicity of radionuclides and the heterogeneous energy deposition make the estimation of the risk following an internal exposure very difficult. As a conclusion, it should be reminded that the effective dose is a tool for the management of radiological protection but not a quantitative indicator of the individual risk. © 2007 EDP Sciences.Protéger l’environnement est aujourd’hui une problématique globale qui concerne toutes les activités de l’homme. Il s’agit donc d’être capable de démontrer la compatibilité de ces activités avec la protection des milieux naturels, mais aussi si nécessaire d’agir pour pallier à un risque potentiel ou avéré, et ce généralement dans le cadre d’une réglementation de plus en plus stricte. Dans le domaine chimique, la prise en compte de cette problématique se traduit par l’existence de méthodes dédiées à l’évaluation du risque environnemental. Dans le domaine radiologique, la nécessité de disposer de tels outils s’est accentuée récemment, afin de pouvoir justifier aux yeux du public et en toute transparence le rejet de substances radioactives dans l’environnement, de répondre aux exigences des nouvelles réglementations en matière de protection de l’environnement et enfin d’harmoniser les approches entre radioprotection humaine et radioprotection de l’environnement, mais aussi entre polluants chimiques et radioactifs, simultanément présents par exemple dans les rejets de routine des centres nucléaires de production d’électricité. Dans cette optique d’harmonisation, les démarches d’évaluation du risque à l’environnement lié à la présence de radionucléides ou de substances chimiques sont présentées depuis les concepts théoriques jusqu’à leur mise en œuvre comparative, approche nouvelle en cours de développement dont les premiers résultats sont présentés

Beneficial arthropod behavior mediated by airborne semiochemicals. III. Influence of age and experience on flight chamber responses of Microplitis demolitor Wilkinson

Heliothis zea (Boddie) larvae fed cowpea seedlings produced volatile semiochemicals to which Microplitis demolitor Wilkinson responded in a wind tunnel. However, most M. demolitor females reared from H. zea larvae fed an artificial diet were not responsive at emergence to the same volatile semiochemicals. A preflight contact with frass from H. zea fed cowpea was needed to stimulate a response of sustained flight in a wind tunnel. The most consistent flight response was 7-10 days postemergence. Response resulting from both antennal and ovipositor contact with host frass during preflight stimulation was no better than from antennal contact alone. Chilling the parasitoid pupae rendered most of the emerging females unresponsive to volatile semiochemicals.F. Hérard, M. A. Keller, W. J. Lewis, J. H. Tumlinso

Beneficial arthropod behavior mediated by airborne semiochemicals. IV. Influence of host diet on host-oriented flight chamber responses of Microplitis demolitor Wilkinson

Microplitis demolitor Wilkinson were reared from Heliothis zea larvae fed either an artificial diet or a diet of cowpea seedlings. Responses of females from these two sources to semiochemicals from the insect host cowpea complex were compared in a flight tunnel. Very limited responses were obtained from females reared from hosts fed artificial diet unless they first had preflight contact with frass from plant-fed hosts. Female parasite is reared from plant-fed hosts were generally responsive without preflight contact. Contact with cocoons containing frass of the plant fed host at the time of emergence was an important source of stimulation. It increased their subsequent responsiveness to the volatile semiochemicals of the insect host-plant complex. The cocoons of females reared from artificial diet-fed hosts were apparently lacking plant chemicals that are vital to their subsequent responsiveness. Imprinting of the adults at time of emergence from the cocoon is strongly indicated.F. Hérard, M. A. Keller, W. J. Lewis, J. H. Tumlinso

An approximate solution of the Riemann problem for a realisable second-moment turbulent closure

mean density p (or #p#) mean pressure T = #p#/### mean temperature E (or mean total energy # entropy # non-viscous part of entropy flux # viscous part of entropy flux # dissipation rate of the turbulent kinetic energy K U i mean velocity in x i direction Correspondencet o: J.M. Herard (e-mail: [email protected] For i =1# 3, and j =1# 3: turbulent Reynolds stress tensor -(U i,j + U j,i U 1,1 # ij ) molecular viscous strain tensor # ij (so-called) pressure strain correlation tensor For i =1# 3, and j =1# 3, and k =1# 3: ## i u ## j u ## k triple velocity correlation Rey1SS stress tensor invariants: I=2K = trace (R) turbulent kinetic energy II R = trace (R ) second invariant of R III R = trace (R ) third invariant of R # i eigenvalues of the Reynolds stress tensor R 1 = R ii first fundamental minor of R (no summation) 2 = R##R ## (R ## ) second fundamental minor of R (no summation); # and # are not equal and not equal

Computation of steam-water transients using a two-fluid seven-equation model

International audienceThis paper is dedicated to the comparison between experimental data and numerical results in multi-phase flows involving high pressure ratios such as water hammer transients. A two-fluid seven equation model has been selected due to its ability to take into account all phasic desequilibria as well as vanishing phases. Theoretical properties of the model are underlined. A mono-dimensional finite volume implementation of the two-fluid model is then compared to the experimental data of the Simpson and Canon experiment. Differences with the classical Baer and Nunziato model are also pointedout

Évaluation de la toxicité chimique des radionucléides à vie longue sur la base des directives de qualité pour l'eau de boisson fixées par l'OMS

L'estimation qui est faite actuellement des risques sanitaires liés à la gestion des déchets nucléaires à vie longue est incomplète si elle ne tient compte que des aspects radiotoxiques. Bien que cette approche soit justifiée à l'égard d'un grand nombre de radionucléides inventoriés, elle ne peut cependant être exclusive et généralisée : la toxicité chimique doit être considérée notamment lorsque la période radioactive d'un radionucléide excède 105 ans. Pour évaluer la toxicité chimique ou radiologique d'un radionucléide, on peut confronter une dose de référence appliquée à la consommation d'eau de boisson (0,1 mSv/an) avec les informations toxicologiques existantes. L'organisation mondiale de la Santé l'a fait pour l'uranium naturel et recommande une valeur guide pour l'eau de boisson, fondée sur sa toxicité chimique (2 μg/l). La démarche adoptée par l'OMS est reprise ici en vue de montrer que la toxicité chimique potentielle d'un élément est une donnée à intégrer dans l'estimation du risque sanitaire des radionucléides à vie longue